(19)
(11)EP 2 714 259 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
02.09.2020 Bulletin 2020/36

(21)Application number: 11739173.0

(22)Date of filing:  26.05.2011
(51)International Patent Classification (IPC): 
B01J 19/00(2006.01)
C08F 2/01(2006.01)
B01J 19/18(2006.01)
C08F 210/12(2006.01)
(86)International application number:
PCT/IT2011/000177
(87)International publication number:
WO 2012/160579 (29.11.2012 Gazette  2012/48)

(54)

POLYMERIZATION REACTOR FOR BUTYL RUBBER PRODUCTION

POLYMERISATIONSREAKTOR ZUR HERSTELLUNG VON BUTYLKAUTSCHUK

RÉACTEUR DE POLYMÉRISATION POUR LA PRODUCTION DE CAOUTCHOUC DE BUTYLE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
09.04.2014 Bulletin 2014/15

(73)Proprietor: Conser S.P.A.
00144 Rome (IT)

(72)Inventors:
  • SIMOLA, Flavio
    I-00015 Monterotondo (RM) (IT)
  • APPETITI, Aldo
    I-00136 Roma (RM) (IT)
  • ANGELETTI, Andrea
    I-00054 Fiumicino (RM) (IT)

(74)Representative: Sarpi, Maurizio et al
Studio Ferrario S.r.l. Via Collina, 36
00187 Roma
00187 Roma (IT)


(56)References cited: : 
WO-A1-96/20777
DE-B- 1 215 936
US-A- 3 737 288
US-A- 3 965 975
US-A- 5 417 930
CA-A- 463 453
US-A- 2 507 105
US-A- 3 790 141
US-A- 4 472 061
US-A- 5 972 661
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to a low temperature polymerization reactor for the production of butyl rubber by catalytic polymerization of isobutylene with small amount of a conjugated diolefin such as isoprene.

    [0002] The single pass tubular reactor is characterized by improved thermal efficiency and improved hydraulic efficiency, in order to permit higher productivity, lower energy consumption and longer reactor cycle time.

    Field of disclosure



    [0003] This invention relates to an improved reactor according to claim 1 for the agitated suspension polymerization of an isoolefin in the presence of a Friedel-Crafts catalyst, to form a suspension or slurry of fine rubber particles in the reaction medium.

    [0004] According to the present invention, the isoolefin polymers are the butyl rubber type polymers, which are prepared by copolymerizing from about 95 to 99.5 mol percent of isobutylene with, correspondingly, from about 5 to 0.5 mol percent of a conjugated diolefin such as isoprene.

    [0005] The polymerization reaction may be conducted at any suitable polymerization temperature such as the temperature range of about -90 to about -105°C.

    [0006] A preferred catalyst is aluminum chloride.

    [0007] The polymerization reaction is conducted with agitation in suspension in a low freezing diluent, typically an alkyl halide such a methyl chloride. The rubber slurry inside the reaction has a rubber content of 20 to 35% by weight. The low temperatures necessary for a satisfactory copolymerization are maintained by heat exchange with a suitable refrigerant such as vaporizing liquid ethylene or liquid methane.

    Background of the invention



    [0008] The copolymer of isobutylene and isoprene, commonly known as butyl rubber (IIR) and the halobutyl rubber (HIIR) derived from butyl rubber by additioln of bromine or chlorine, are extensively used in several applications, being the tire manufacture the major. In the prior art several inventions have been applied to the design of the polymerization reactor for the production of the butyl rubber.

    [0009] US serial No. 448,575, filed June 26,1942 then abandoned, and CA 463453 both by John H. Bannon may be considered among the first applications on the concept of the tubular polymerization reactor. In this reactor a draft tube provided with an agitator is arranged centrally of the reactor and a plurality of return tubes are arranged between headers and around the central draft tube, with means for circulating a suitable refrigerant, desirably vaporizing ethylene, through the space between the headers and around the central draft tube as well as the return tubes.

    [0010] A back-mixed reactor is employed; typically a one-tube pass system as described by reference to U.S. Pat. No. 2,474,592. Such reactor consists of a vertical vessel formed by an enclosing side wall within which is provided an axially mounted draft tube of relatively large diameter surrounded by large number of small diameter tubes which extend downwardly. An axial flow pump, which extends into the draft tube is located in the bottom of the reactor to pump the reaction mixture up the draft tube. The reaction mixture includes the diluents, catalyst and reactants, which are directly introduced into the bottom of the reactor, and a portion of the reaction mixture which after up flowing through the draft tube is recycled from the top of the reactor downwardly through the tubes which surround the draft tube. The outer walls of the reaction vessel form a jacket through which a liquid hydrocarbon coolant is circulated to remove the exothermic heat of reaction via heat exchange contact with the outer walls of the small diameter tubes, and wall of the central draft tube.

    [0011] US patents 2,577,856 and its continuation-in-part application US 2,636,026 represent a different version of the vertical shell and tube reactor, in which the central draft tube provided with an impeller is surrounded, rather than by several smaller tubes, by concentric annular surfaces, continually withdrawing heat from the annular walls by indirect heat transfer with a coolant circulating in one or more annular chambers. The second patent describes a serious problem encountered in each commercial tubular reactor, due to accumulation of polymer on the upper entrance tube sheet and plugging of the return tubes, especially at their entrance ends; the trouble is general and persistent under widely varying conditions of operation.

    [0012] US patent 2,999,084 concerns the use of the vertical tubular reactor with the central draft tube, wherein the improvement comprises the injection of the feed solution containing isobutylene/isoprene in methyl chloride at a zone of higher stream velocity immediately below the propeller. The patent refers that in commercial experience the mass fouling is a limiting factor of prime importance with respect to the rate of production of butyl rubber polymer; fouling inhibits adequate refrigeration and is the reason of the operation of the reactor in run having intervals within the range of about 10 to 90 hours; cleaning out the reactor before resuming the polymerization reaction normally requires 10 to 20 hours.

    [0013] European patent EP0053585 proposes a different type of polymerization reactor suitable for the production of butyl rubber at a temperature ranging from -40 to -110 °C. The reactor incorporates an internal rotary coolant chamber, a coaxial agitator and an external cooling jacket. The outer and inner faces of the rotary chamber are kept clean by rotating scrapers.

    [0014] Even if this type of reactor can keep the heat exchange surfaces free from rubber deposits, it has the disadvantage of a limited exchange surface and therefore of a limited productivity.

    [0015] The European patent EP0209253 describes a still fully different polymerization reactor and process, in which the monomers mixture of isobutylene and isoprene together with a polymerization medium, consisting in a mixture of halogenated and not halogenated hydrocarbons, is polymerized in a self cleaning screw extruder at a temperature of -50 to +15 °C, somewhat higher than prior art close to -100 °C. Heat of polymerization is removed by evaporative cooling of the reaction medium. Even if of academic interest, this application, due to the high reaction temperature, is not able to produce butyl rubber acceptable by the market and it has not been used industrially.

    [0016] The Russian patents RU1615935 and RU2097122 propose a reactor applicable for butyl rubber, wherein the arrangement of the polymerization slurry and the cooling medium is the opposite compared with the conventional vertical tubular reactor with central draft tube: the polymerization reaction occurs in the shell of the vessel, supplied with a central multiple blades stirrer, while the refrigerating ethylene passes through vertical tube bundles (four in the patent drawings) peripherally disposed and put in from the upper head of the reactor. A drawback of this invention is the high asymmetric arrangement, due to the position of the tube bundles, and the highly not homogeneous velocity of the rubber slurry inside the reactor vessel.

    [0017] In spite of the alternative reactor arrangements described in the above mentioned and in other patents, as reported in the Ullmann's-Encyclopedia of Industrial Chemistry-fifth edition, the most used industrial reactor corresponds to the vertical tubular reactor with draft tube model, as proposed in the original US serial No. 448,575 and better defined in US2,474,592 and US2,999,084.

    [0018] Whereas this reactor has been commercially used by the industry for many years for conducting these types of reactions, the reactor is less efficient than desirable.

    [0019] Effective agitation is of particular importance in that the polymerization reaction is exothermic and in that the molecular weight of the polymer product is adversely affected by increases in temperature. Thus, when the reaction medium is not of an entirely homogeneous composition, localized overheating may occur, resulting in the formation of undesirable polymeric materials which adhere tenaciously to metal surfaces within the reaction vessel. This phenomenon, commonly referred to as mass fouling, has presented a problem with respect to the production of butyl rubber.

    [0020] Moreover, a gradual and uniform buildup of polymer deposits upon and fouls the heat transfer surfaces within the reaction vessel; the polymer adheres to the metal surfaces as a continuous film. Nevertheless, polymer fouling presents a problem and, in consideration of the downtime to remove the fouling, it has limited the efficiency of this type of reactor, as also reported in the above mentioned US patent 2,999,084.

    [0021] In U.S. Pat. No. 5,417,930, Exxon describes a new model of butyl rubber tubular reactor, without the draft tube and having a reduced fouling tendency compared with the older conventional type of reactor with central draft tube, as described in U.S. Pat. No. 2,999,084 and in other patents.

    [0022] The reactor contains a two-tubes pass system, constituted of an inner or center tube bundle, through which a mixture or slurry of polymerizable monomers, diluent and catalyst is passed in one direction and recycled via an outer tube bundle in the opposite direction in essentially even flow distribution.

    [0023] The tubular bundles are maintained within a jacketed section, where a refrigerant removes the exothermic heat of reaction from the polymerization mixture and maintains the polymerization mixture at uniformly low temperature. An even flow circulation of the slurry, which aids in maintaining uniform low temperature, is provided by the use of a diffuser and mixed flow pumping system.

    [0024] The proposed model is more complex than the conventional reactor and further subject of limiting factors.

    [0025] In fact while it may be agreed in principle that the flow distribution in the inner tube bundle will be uniform, such uniformity does not appear to be granted for what concerns the flow distribution in the outer tube bundle.

    [0026] Furthermore the pressure drop in the two-tube pass design will be higher compared with the conventional simple-pass design.

    [0027] The US Pat. No. 4,472,061 A discloses a single pass shell and tubes type polymerization reactor, suitable to produce butyl rubber in slurry, by copolymerizing at least 95% of isobutylene with no more than about 5 wt % of isoprene in concentration of about 35 to 45% by vol. in a solvent in presence of 0.015% to 0.15% by weight of catalyst. According to the invention in the reactor an inlet port introduces the reaction mixture at a bottom side near an impeller shaft and an outflow port is located in the top; a cooling media in the shell side removes the heat of reaction; the impeller acting as circulation pump is installed at the bottom and permit high velocity of the rubber slurry in the central draft tube and in downflow smaller tubes. Such reactor further comprises:
    1. a. an extended upper head,
    2. b. an hemispheric bottom head with fluid deflectors,
    3. c. a straightening baffles.


    [0028] The US Pat. No. 3,737,288 A discloses a fluidized bed reactor wherein olefins are polymerized or copolymerized in a bed formed by particles being polymerized and fluidized with the aid of a circulating gas. In the reactor, a circulating gas is fed from a gas space above the fluidized bed into the lower part of the reactor. The lower part of the reactor includes an annular space having an defined by an upwards tapering rotating conical surface and an outer wall defined by a downwards tapering rotating conical surface. In the upper head of said reactor there are a draft tube and a deflector establish a field or pattern of agitation to cause shear thinning and upflow throughout the draft tube and which may produce turbulence at the liquid surface. A plurality of radially inwardly projecting, circumferentially spaced baffles extend from the draft tube and are proximate the mixing impellers to prevent swirling of the liquid within the draft tube.

    [0029] The US Pat. No. 3,965,975 relates to improvements in horizontal, continuously internally circulating contacting-mixing devices of the type having an impeller, a circulating tube and (usually) an indirect heat exchanging tube bundle; providing several baffles arrangement types with a disc or doughnut shape which can be placed in a reactor enhancing and optimizing mass and heat transfer. These and other considerations show that there is a need for better design of a single pass reactor for the production of the butyl rubber.

    SUMMARY OF THE INVENTION



    [0030] The present invention concerns an improved design of a single pass shell and tubes reactor as defined in claim 1, herewith shown in Fig. 1, for the production of butyl rubber, characterized by a superior design of thermal and hydraulic efficiency compared with the conventional type of reactor (Fig.1a) described in U.S. Pat. No. 2,999,084.

    [0031] The improvements are reached by the following combinations:

    a) an extended upper head with fluid deflector wherein the shape of the head and of the deflector are optimized in order to reach a very homogeneous slurry velocity in the rows of tubes and to minimize the pressure drop due to the inversion of flow from up-flow to down-flow and to the entrance of the slurry in the tubes; the better performance is achieved increasing the top zone eight and guiding the fluid in its curve by installing fluid deflector fixed to the top tube-sheet.

    b - an hemispheric bottom head with fluid deflectors placed between the impeller and the bottom itself and designed to minimize the pressure drop due to the inversion of flow from down-flow to up-flow;

    c - straightening baffles inside the draft tube, which shape and dimensions are optimized to turn the radial velocity components produced by the rotation of the impeller into axial velocity components,
    wherein such innovations, improving substantially the homogeneity of the velocity and reducing the overall pressure drop, allow an increased circulation in the bottom pump and longer reactor cycles.



    [0032] The straightening baffles are designed as surfaces with a lower curved part and an upper straight radial part and the curved parte is constructed (trying to be almost tangent to the velocity field after the impeller in the lower part and vertical in the upper part) as a sequence of radial segments: starting from the bottom and going upwards each one has an increasing angular coordinate together with an increasing axial coordinates.

    [0033] As a consequence of the innovative design of a single pass reactor as above described, the following results are achieved:

    A - Thermal efficiency



    [0034] 

    a1 - Higher tube side (rubber slurry) heat transfer, thanks to the higher and more homogeneous slurry velocity in the tubes.

    a2 - Higher shell side (vaporizing ethylene) heat transfer, by using internal baffles.

    a3 - Slower increase of the fouling factor in the tube side during the reactor run.


    B - Hydraulic efficiency



    [0035] 

    b1 - The new shape of the upper head and of the fluid deflector, in addition to permit to reach a very homogeneous slurry velocity in the rows of tubes and to minimize the pressure drop due to the inversion of flow from up-flow to down-flow and to the entrance of the slurry in the tubes, minimizes also the vortex at the entrance of the tubes and eliminated the bad slurry distribution (velocity nearly to zero in the external part of the tubes) occurring in the old design reactors.

    b2 - The presence of an hemispheric bottom head with fluid deflectors, satisfy the requirement of a straight flow field at the end of the draft tube while the high turbulent intensity zones are only after the impeller zone.

    b3 - Straightening baffles in the draft tube, avoid the possible pseudo-helicoidal motion inside the draft tube generated by the rotation of the impeller, allowing an increased hydraulic efficiency.


    Brief Description of the Figures



    [0036] A better understanding of the invention will be obtained by considering the detailed description below, with reference to the following drawings in which:

    Fig. 1 is a sectional view of the reactor according to the present invention for the production of butyl rubber;

    Fig.1a is a sectional view of a conventional polymerization reactor for the same production;

    Fig.2 is the detail of the shaped top deflector of Fig.1;

    Fig.3 is the detail of the shaped bottom deflector of Fig.1;

    Fig.4 is the detail of the straigtening baffles inside the draft tube of Fig.1

    Fig.5 is the detail of the disc and doughnut baffles in the shell side of Fig.1.



    [0037] Reference is made to a polymerization reactor 1 in which the rubber slurry circulates according to the flow directions 9 inside four rows of vertical pipes 6 (from the top to the bottom) and a draft tube 2 (from the bottom to the top), pushed by a rotating impeller 5 put in the lower part of the draft tube. All these parts are included in a cylindrical vessel with two curved heads.

    [0038] The reacting fluid 10 is introduced from the bottom side near the impeller shaft, while the outflow 11 is on the top.

    [0039] The recirculating volumetric flow rate is of 500 to 600 times greater than the inflow rate.

    [0040] In the top region the flow must invert its direction coming from the draft tube and going into the pipe rows. In the conventional draft tube reactor, this inversion is quite dissipative as it happens in a short distance without a guide to the flow. The direction of the fluid at the pipes inlet has a big radial component not aligned with the pipes axis; this produces a not uniform distribution of the flow among the pipes, with the external pipes velocity almost double respect to the inner ones and a relevant pressure loss at the pipes inlet (together with the inversion zone).

    [0041] In order to improve the performances of the reactor, shape modifications have been introduced to reach the target of re-equilibrating the flow among the pipe rows (trying to reach an homogeneous mean velocity) and reducing the pressure drop in the top zone.

    [0042] The results of optimization show that a better performance can be achieved increasing the top zone height (because the fluid has more space to change its direction without strict deviations from the boundary and arriving at the pipes inflow more vertical) and guiding the fluid in its curve reducing vortices and turbulent dissipation, by installing shaped flow conveyors 15 fixed to the top tube-sheet 14, as shown in Fig. 2.

    [0043] As global results it can be noticed that: as for the first target of an homogeneous mean velocity through the pipes, the maximum distance from the mean value has passed from around 40% to 5% or less, as for the second target of a lower pressure drop, evaluating the differential of total pressure from inflow to outflow (that is the specific energy that the impeller should give to the fluid to reach the design mass flow rate) it has been reduced in a very significant way.

    [0044] Concerning the optimization of the bottom part of the reactor, in order to satisfy the requirement of a straight flow field at the end of the draft tube, a deflector after the impeller has been provided. The impeller not only impresses a tangential velocity component (increasing the velocity magnitude and so the dissipation), but also is an intense turbulence source, so the pressure loss is definitely increased.

    [0045] The basic criteria in optimization the bottom part is to provide more space to the flow to change its direction from downwards to upwards and guiding it in order to reduce chaotic streams and separations. The best results have been reached by using a simple semispherical head 4. This objective is further achieved by installing at bottoms shaped deflectors 17 and 18 fixed to the bottom tube-sheet 16 (fig.3) and straightening baffles 7 inside the draft tube 2 as shown in Fig. 4.

    [0046] As a result of these innovations the flow field in the bottom part is much more regular, without separations, the total pressure is more uniform, the high turbulent intensity zones are only after the impeller zone; all these features lead not only to lower pressure losses in the bottom part but also to a considerable increase of the pressure gain provided by the impeller that is better exploited because of a more uniform velocity distribution at the suction side.

    [0047] Moreover the increased efficiency of the impeller permits also a reduced amount of the heat load to be removed by the reactor refrigerant and, therefore, the saving in energy consumption is twofold.

    [0048] The rotation of the impeller induces tangential velocity component to the flow that, without any conditioning, would generate a pseudo-helicoidal motion inside the draft tube (with the mass flow rate mainly on the outer part due to centrifugal force).

    [0049] To remove this effect the straightening baffles 7, introduced in the draft tube as shown in Fig. 4, has been designed as three surfaces with a periodicity of 120° and with a lower curved part and an upper straight radial part. The curved part has been constructed trying to be almost tangent to the velocity field after the impeller in the lower part and vertical in the upper part.

    [0050] Another innovative aspect of this invention refers to the arrangement of the cooling system in the shell side 19 of the tubular reactor 1. In all the industrial applications of the reactors for manufacturing butyl rubber the heat of polymerization, plus the heat generated by the rotating impeller, is removed by a circulation of vaporizing ethylene through a flash drum, normally located in a position above the reactor shell , in order to have the proper static differential head to balance the pressure losses, static and frictional, and to permit a thermosiphon circulation.

    [0051] As a consequence of this liquid head, the point of initial vaporization deviates appreciably from the reactor jacket inlet point; in other terms the liquid ethylene 12 entering the reactor shell is normally in conditions of sub-cooling and the bottom part of the reaction is to preheat such liquid up to the real boiling temperature.

    [0052] In a conventional butyl reactor the impact is very detrimental and substantially reduces the heat transfer efficiency and capacity; being the full area of the jacket available for the liquid, the resulting liquid ethylene velocity is very low and the resulting heat transfer coefficient is much lower than the value expected in vaporizing conditions.

    [0053] This drawback may be overcome by using cross baffles 8, in order force the flow according to direction 20 and to permit an increased velocity and heat transfer coefficient of the refrigerant fluid. In consideration of the different degree of vaporization along the reactor height, with no vaporization at the inlet 12 and the lower part of the reactor and maximum vaporization at the outlet 13, the spacing between two consecutive baffles is not fixed and it is also changing with the reactor height.

    [0054] Segmental, double segmental or disc 21 and doughnut 22 baffles may be used, being the last type, as shown in Fig. 5, the preferred one for this application.

    EXAMPLES


    COMPARATIVE EXAMPLE 1



    [0055] A conventional tubular, draft tube type reactor for the production of around 2.7 ton/hr of butyl rubber with Mooney viscosity of around 51 (ML 1+8 at 125 °C) has been subject to a Computational Fluid Dynamics (CFD) technique by using the commercial software by Fluent Inc.

    [0056] The reactor, herewith represented in Fig 1a, is a shell and tube vertical exchanger, with the reaction in the tube side and vaporizing ethylene as cooling medium in the shell side, to remove the exothermic heat of polymerization. The reactor includes a rotating impeller installed at the bottom, in the lower part of the central draft tube. The draft tube is surrounded by 120 vertical pipes, six meters length, disposed in four concentric rows. The reacting mixture is introduced from the bottom side, near to the impeller shaft, while the slurry product is drawn-off from a nozzle in the upper head. Both the bottom and top heads are of the standard semi-elliptical type.

    [0057] The results of the different simulations showed different drawbacks of this type of reactor, as follows:
    • an evident not uniform distribution of the flow among the pipes, with the external pipes velocity almost double respect the inner ones.
    • the distribution of the velocity vectors inside the reactor shows that, in the top head, the slurry coming from the draft tube, due to the sudden inversion of the flow, knocks into the wall of the semi-elliptical head and the flow preferentially close to the same wall in a radiate motion, from the center to the external part of the reactor. Therefore the slurry arrives to the upper tube sheet mostly from its external part. This behavior entails two negative consequences, as follows:
      1. a. the velocity of the slurry in the external rows is much higher than in the central rows, as already described
      2. b. the rubber slurry enters the pipes tangentially rather than axially: this fact creates a large vortex at the inlet of the pipes with an evident not uniform velocity inside each pipe; here the slurry flows preferentially in the part of the pipe toward the center of the reactor, while the part of the pipe toward the external reactor wall has a velocity near to zero, promoting in this way the deposit of sticky rubber.


    [0058] This result of the fluid-dynamic analysis, summarized in Table I confirms the experimental phenomenon described more than 50 years ago in the mentioned US patent 2,636,026 (plugging of the reactor tubes, especially at their entrance ends).
    TABLE I Conventional tubular reactor
    Average velocity in the pipes, m/s 2.92
    Velocity distribution: 
    1st row, m/s 2.25
    2nd row, m/s 2.00
    3rd row, m/s 2.85
    4th row, m/s 4.05
    Total reactor pressure drop, KPa 29

    EXAMPLE 2



    [0059] The example 2 represents an application of the improved reactor according to the present invention, as represented in Fig.1.

    [0060] The same reactor described in example 1 with 120 tubes has been improved by:
    • an extended upper head with fluid deflector
    • a semispherical bottom head with fluid deflectors
    • three straightening baffles in the draft tube The combined effect of the above described modifications permits, even together with a reduced power consumption of the impeller, an higher average velocity, a more uniform distribution of the velocity in all parts of the reactor and a reduced pressure drop, as shown in Table II:
    TABLE II- Improved tubular reactor
    Average velocity in the pipes, m/s 3.26
    Velocity distribution: 
    1st row, m/s 3.22
    2nd row, m/s 3.23
    3rd row, m/s 3.22
    4th row, m/s 3.37
    Total reactor pressure drop, KPa 20



    Claims

    1. A single pass shell and tubes type polymerization reactor (1), used to produce butyl rubber in slurry, copolymerizing at least 95 wt% of isobutylene with not more than 5 wt% of isoprene, in concentration of 35 to 45% by vol. in a solvent, preferably methyl chloride, in presence of 0.015% to 0.15% by weight of catalyst, preferably aluminium chloride, and at a temperature within the range of - 104°C to -90°C, wherein the velocity in the tubes is the range from 2.4 to 4.5 m/sec, with the reaction in tube side and a cooling media in the shell side (19) to remove the heat of reaction, wherein:

    - the slurry circulates inside the tubes (6) and a central draft tube (2) pushed by a rotating impeller (5) in the lower part of the draft tube to permit high velocity of the rubber slurry in the central draft tube (2) and in downflow smaller tubes (6), and

    - the reaction mixture (10) is introduced from the bottom side near the impeller shaft (5) and the outflow (11) is in the top,

    characterized in that the reactor (1) comprises:

    a - an extended upper head (3) containing a fluid deflector (15), according to figure 2, wherein the shape of the head and of the deflector are sized to reach a very homogeneous slurry velocity in the rows of tubes (6) and to minimize the pressure drop due to the inversion of flow from up-flow to down-flow and to the entrance of the slurry in the tubes (6); the vortex at the entrance of the tubes being also minimized, while is eliminated any bad slurry distribution;

    b - an hemispheric bottom head (4) with a first fluid deflectors (17) and a second fluid deflector (18), both according to figure 3 and, sized to minimize the pressure drop due to the inversion of flow from down-flow to up-flow;

    c - three straightening baffles (7) in the draft tube (2), having a periodicity of 120° and designed as surfaces with a lower curved part and an upper straight radial part and the curved part is constructed as a sequence of radial segments starting from the bottom and going upward each one having an increased angular coordinate together with an increasing axial coordinates in order to turn the radial
    velocity components produced by the rotation of the impeller (5) into axial velocity components, allowing an increased hydraulic efficiency, thereby, improving the homogeneity of the velocity and reducing the overall pressure drop, and allowing an increased circulation in the bottom pump and longer reactor cycles.


     
    2. A reactor as in claim 1, wherein the extended upper head (3) is obtained increasing the top zone height.
     
    3. A reactor as in claim 1, wherein the fluid deflector (15) is fixed to the top tube-sheet (14) and the bottom deflectors (17, 18) are fixed to the bottom tube-sheet (16).
     
    4. A reactor as in claim 1, further comprising a plurality of cross baffles (8) in the jacket side (19) for the circulation of the liquid coolant, which is either ethylene or methane, with single or plurality of nozzles for the removal of the coolant circulating at a temperature ranging from -120 to -100°C.
     
    5. A reactor as in claim 4, wherein the cross baffles (8) are of the disc (21) and doughnut (22) type and therefore apt to force the flow according to direction (20) and to permit an increased velocity and heat transfer coefficient of the refrigerant fluid.
     
    6. A reactor as in claim 5, wherein, in consideration of the different degree of vaporization along the reactor height, with no vaporization at the inlet (12) and the lower part of the reactor and maximum vaporization at the outlet (13), the spacing between two consecutive baffles (8) is not fixed and it is also changing with the reactor height.
     
    7. A reactor as in claim 1, wherein the single pass tubes are located in from 2 to 8 rows, preferable from 3 to 5 rows.
     


    Ansprüche

    1. Ein Polymerisationsreaktor (1) vom Typ mit Mantel und Rohren, welcher dazu eingesetzt wird Butylkautschuk in Aufschlämmung herzustellen, Copolymerisation von mindestens 95 Gew.-% Isobutylen mit nicht mehr als 5 Gew.-% Isopren in etwa 35 bis 45 Vol.-% in einem Lösungsmittel, vorzugsweise Methylchlorid, in Gegenwart von 0,015 bis 0,15 Gew.-% Katalysator, vorzugsweise Aluminiumchlorid, und bei einer Temperatur im Bereich von -104°C bis -90°C, wobei die Geschwindigkeit in den Rohren im Bereich von 2,4 bis 4,5 m/sec liegt, mit der Reaktion in der Rohrseite und einem Kühlmedium in der Mantelseite (19), um die Reaktionswärme abzuführen, wobei:

    - der Schlamm innerhalb der Rohre (6) und einem zentralen Saugrohr (2) durch Anschub eines im unteren Bereich des Saugrohrs installierten Laufrades (5) zirkuliert, um eine hohe Geschwindigkeit der Kautschukaufschlämmung im zentralen Saugrohr (2) und in nach unten gerichteten kleineren Rohren (6) zu ermöglichen, und

    - die Reaktionsmischung von der Bodenseite nahe dem Laufradrohr (5) erfolgt und der Ausfluss (11) im Kopfbereich ist,

    dadurch gekennzeichnet, dass der Reaktor (1) umfasst:

    a - einen verlängerten oberen Kopf (3) mit einem Fluiddeflektor (15), wobei die Form des Kopfes und des Deflektors optimiert sind, um eine sehr homogene Schlammgeschwindigkeit in den Rohrreihen (6) zu erreichen und den Druckabfall aufgrund der Umkehrung der Strömung von Aufwärtsströmung zu Abwärtsströmung und zum Eintritt des Schlamms in die Rohre (6) zu minimieren; wobei der Wirbel am Eingang der Rohre ebenfalls minimiert wird, während jedwede schlechte Schlammverteilung vermieden wird;

    b - ein halbkugelförmiger Bodenkopf (4) mit einem ersten Fluiddeflektor (17) und einem zweiten Fluiddeflektor (18), die beide gemäß Figur 3 konstruiert sind und so dimensioniert sind, dass der Druckabfall aufgrund der Umkehrung der Strömung von der Abwärtsströmung zur Aufwärtsströmung minimiert wird;

    c - drei Richtbleche (7) im Saugrohr (2) mit einer Periodizität von 120° und als Oberflächen mit unteren gebogenen Teilen und einem oberen gerade radialen Teil, wobei der gebogene Teil als eine Sequenz von radialen Segmenten konstruiert ist, die vom Boden anfangen und jeweils aufwärts ragen, so dass jeder eine erhöhte Winkelkoordinate zusammen mit sich erhöhenden Achskoordinaten hat, um die durch die Rotation des Laufrades (5) erzeugten radialen Geschwindigkeitskomponenten in axiale Geschwindigkeitskomponenten umzuwandeln, wodurch ein erhöhter hydraulischer Wirkungsgrad ermöglicht wird, und deshalb die Homogenität der Geschwindigkeit wesentlich verbessert, der Gesamtdruckabfall verringert und eine erhöhte Zirkulation in der Bodenpumpe und längere Reaktorzyklen ermöglicht werden.


     
    2. Ein Reaktor nach Anspruch 1, wobei der verlängerte obere Kopf (3) erhalten wird, indem die Höhe der oberen Zone vergrößert wird.
     
    3. Ein Reaktor nach Anspruch 1, wobei der Flüssigkeitsdeflektor (15) an der oberen Rohrplatte (14) und die Bodendeflektoren (17, 18) an der unteren Rohrplatte (16) befestigt sind.
     
    4. Ein Reaktor nach Anspruch 1, weiterhin umfassend eine Vielzahl von Querleitblechen (8) in der Mantelseite (19) für die Zirkulation des flüssigen Kühlmittels, das entweder Ethylen oder Methan ist, mit einzelnen oder mehreren Düsen für die Entfernung des Kühlmittels, das bei einer Temperatur im Bereich von -120 bis -100°C zirkuliert.
     
    5. Ein Reaktor nach Anspruch 4, wobei die Vielzahl von Querleitblechen (8) vom Scheibentyp (21) und Doughnuttyp (22) sind und daher dazu geeignet sind, die Strömung gemäß der Richtung (20) zu erzwingen und eine erhöhte Geschwindigkeit und einen erhöhten Wärmeübertragungskoeffizienten des Kühlfluids zu ermöglichen.
     
    6. Ein Reaktor nach Anspruch 5, wobei unter Berücksichtigung des unterschiedlichen Grades der Verdampfung entlang der Reaktorhöhe, ohne Verdampfung am Einlass (12) und dem unteren Teil des Reaktors und mit maximaler Verdampfung am Auslass (13), der Abstand zwischen zwei aufeinanderfolgenden Blechen (8) nicht fixiert ist und sich auch mit der Reaktorhöhe ändert.
     
    7. Ein Reaktor nach Anspruch 1, bei dem die einzelnen Durchgangsrohre in 2 bis 8 Reihen, vorzugsweise in 3 bis 5 Reihen, angeordnet sind.
     


    Revendications

    1. Réacteur de polymérisation de type multitubulaire à calendre à un passage (1), utilisé pour produire du caoutchouc butyle en bouillie, en copolymérisant au moins 95 % en poids d'isobutylène avec pas plus de 5 % en poids d'isoprène, en concentration de 35 à 45 % en volume dans un solvant, de préférence du chlorure de méthyle, en présence de 0,015 % à 0,15 % en poids de catalyseur, de préférence du chlorure d'aluminium, et à une température dans la plage de -104 °C à -90 °C, dans lequel la vitesse dans les tubes est dans la plage de 2,4 à 4,5 m/s, avec la réaction dans le côté tube et un agent de refroidissement dans le côté calendre (19) pour enlever la chaleur de réaction, dans lequel :

    - la bouillie circule à l'intérieur des tubes (6) et d'un tube d'aspiration central (2) poussée par un rouet rotatif (5) dans la partie inférieure du tube d'aspiration pour permettre une vitesse élevée de la bouillie de caoutchouc dans le tube d'aspiration central (2) et dans des tubes plus petits à écoulement descendant (6), et

    - le mélange de réaction (10) est introduit depuis le côté de dessous près de l'arbre de rouet (5) et l'écoulement sortant (11) est dans le dessus,

    caractérisé en ce que le réacteur (1) comprend :

    a - une tête supérieure étendue (3) contenant un déflecteur de fluide (15), selon la figure 2, dans lequel la forme de la tête et du déflecteur est dimensionnée pour atteindre une vitesse de bouillie très homogène dans les rangées de tubes (6) et pour minimiser la chute de pression due à l'inversion d'écoulement d'un écoulement ascendant à un écoulement descendant et à l'entrée de la bouillie dans les tubes (6) ; le tourbillon à l'entrée des tubes étant également minimisé, tandis qu'est éliminée toute mauvaise distribution de bouillie ;

    b - une tête de dessous hémisphérique (4) avec un premier déflecteur de fluide (17) et un second déflecteur de fluide (18), tous les deux selon la figure 3 et, dimensionnée pour minimiser la chute de pression due à l'inversion d'écoulement d'un écoulement descendant à un écoulement ascendant ;

    c - trois chicanes de redressement (7) dans le tube d'aspiration (2), ayant une périodicité de 120° et conçues en tant que surfaces avec une partie incurvée inférieure et une partie radiale droite supérieure et la partie incurvée est construite comme une suite de segments radiaux partant du dessous et allant vers le haut ayant chacun une coordonnée angulaire accrue conjointement avec des coordonnées axiales croissantes afin de changer les composantes de vitesse radiale produites par la rotation du rouet (5) en composantes de vitesse axiale, permettant une efficacité hydraulique accrue, améliorant ainsi l'homogénéité de la vitesse et réduisant la chute de pression globale, et permettant une circulation accrue dans la pompe de dessous et des cycles de réacteur plus longs.


     
    2. Réacteur selon la revendication 1, dans lequel la tête supérieure étendue (3) est obtenue par augmentation de la hauteur de zone de dessus.
     
    3. Réacteur selon la revendication 1, dans lequel le déflecteur de fluide (15) est fixé à la calendre de tube de dessus (14) et les déflecteurs de dessous (17, 18) sont fixés à la calendre de tube de dessous (16).
     
    4. Réacteur selon la revendication 1, comprenant en outre une pluralité de chicanes transversales (8) dans le côté chemise (19) pour la circulation du fluide caloporteur liquide, qui est de l'éthylène ou du méthane, avec une seule buse ou une pluralité de buses pour l'enlèvement du fluide caloporteur circulant à une température dans la plage de -120 à -100 °C.
     
    5. Réacteur selon la revendication 4, dans lequel les chicanes transversales (8) sont du type à disque (21) et couronne (22) et par conséquent aptes à forcer l'écoulement selon la direction (20) et à autoriser une vitesse et un coefficient de transfert de chaleur accrus du fluide frigorigène.
     
    6. Réacteur selon la revendication 5, dans lequel, compte tenu du degré de vaporisation différent selon la hauteur de réacteur, sans vaporisation au niveau de l'orifice d'entrée (12) et de la partie inférieure du réacteur et avec une vaporisation maximale au niveau de l'orifice de sortie (13), l'espacement entre deux chicanes (8) consécutives n'est pas fixe et change également avec la hauteur de réacteur.
     
    7. Réacteur selon la revendication 1, dans lequel les tubes à un passage sont situés dans 2 à 8 rangées, de préférence 3 à 5 rangées.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description




    Non-patent literature cited in the description